Solubilized polymer concentrates, methods of preparation thereof, and well drilling and servicing fluids containing the same

ABSTRACT

The invention provides concentrates for reducing the fluid loss on an oil base well drilling or servicing fluid, the concentrates comprising an oleagineous liquid and (1) a polymer which is solublized in the oleagineous liquid, or (2) a polymer which is solublized in the oleaginous liquid together with an organophilic polyphenolic material which is solublized and/or dispersed in the oleagineous liquid. The method of preparing the concentrate and the method of reducing the fluid loss of an oil base well drilling or servicing fluid utilizing the concentrates is also disclosed. The preferred oil soluble polymer is a styrene-butadiene rubber crumb. The preferred oleagineous liquid is an aromatic-free hydrogenated oil essentially containing only saturated hydrocarbons. The preferred polyphenolic material is a source of humic acid, such as mined lignite.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a continuation of U.S. Non-Provisional applicationSer. No. 13/971,697, filed Aug. 20, 2013, which is a non-provisional ofU.S. Provisional Patent Application Ser. Nos. 61/691,039, filed Aug. 20,2012. Priority is claimed to these applications, and they areincorporated herein by reference in their entireties.

FIELD OF THE INVENTION

The inventions disclosed and taught herein relate generally to oil-basedwell drilling and servicing fluids. More particularly, the inventionsrelate to all-oil and invert oil emulsion well drilling, servicing andtreating fluids containing an oil-soluble polymeric fluid loss controladditive solubilized therein.

BACKGROUND

This invention relates to oil base well drilling and servicing fluids.In particular, the invention relates to “all-oil” and “invert oil”emulsion well drilling and servicing fluids containing an oil-solublepolymeric fluid loss control additive solubilized therein.

As is well known in the art, invert emulsion oil based well drilling andservicing fluids, generally called “muds”, are water-in-oil emulsionsthat typically contain an organophilic clay viscosifier/suspensionadditive, and a weighting agent. The water phase is usually a solutionof a salt, such as calcium chloride or sodium chloride, whoseconcentration is normally adjusted such that the aqueous activity of thefluid is equal to or less than the aqueous activity of the subterraneanformations contacted by the fluids. This minimizes transfer ofwater-to-water-sensitive formations and maintains a stable wellbore.

The invert emulsion is usually stabilized with a “primary emulsifier”,often a fatty acid or salt thereof, while the weighting material and thesolids the fluid acquires during use are made oil-wet and dispersed inthe fluid with a “secondary emulsifier”, typically a strong wettingagent such as a polyamide, amido-amine (partial amide of a polyamine),and the like.

Regardless of whether it is an all-oil, or an invert fluid, drillingfluids, or ‘drilling muds’ as they are sometimes called, are slurriesused in the drilling of wells into the earth for the purpose ofrecovering hydrocarbons and other fluid materials. Drilling fluids havea number of functions, the most important of which include lubricatingthe drilling tool and drill pipe which carries the drilling tool,removing formation cuttings from the well, counterbalancing formationpressures to prevent the inflow of gas, oil or water from permeablerocks which may be encountered at various levels as drilling continues,and holding the cuttings in suspension in the event of a shutdown in thedrilling and pumping of the drilling fluid.

For a drilling fluid to perform these functions and allow drilling toprogress, the drilling fluid must stay in the borehole during thedrilling operation. Frequently, undesirable formation conditions areencountered in which substantial amounts, or in some cases, practicallyall of the drilling fluid may be lost to the formation. Drilling fluidcan leave the borehole through large or small fissures or fractures inthe formation or through a highly porous rock matrix surrounding theborehole.

Most subterranean wells are drilled with the intent of forming a filtercake of varying thickness on the sides of the borehole. The primarypurpose of the filter cake is to reduce the large losses of drillingfluid to the surrounding formation. Unfortunately, formation conditionsare frequently encountered which may result in unacceptable losses ofdrilling fluid to the surrounding formation despite the type of drillingfluid employed and filter cake created.

Well drilling and servicing fluids typically contain an additive tocontrol the loss of fluid to the formation being drilled or serviced. Avariety of different substances have been used and are pumped down wellbores in an attempt to reduce the large losses of drilling fluid tofractures and the like in the surrounding formations. Typical fluid losscontrol additives for use with oil base fluids are gilsonite, asphalt,oxidized asphalt, cellulose-based materials and various polymers, aswell as almond, walnut, and other nut hulls. These fluid-loss controlagents are added to the drilling or servicing fluid in an attempt toreduce the unacceptable high losses of drilling or servicing fluid tofractures and/or porous structures in the surround formation.

A number of issued patents over the years have described variouspolymeric compositions as fluid loss control additives in oil base muds.For example, U.S. Pat. No. 2,697,071 to Kennedy, et al. describes theuse of rubber latex to regulate the viscosity and fluid loss of oil basemuds.

U.S. Pat. No. 2,743,233 to Fisher describes drilling muds, and improvedmethods of drilling wells in the earth. Preferred embodiments of theinvention reportedly relate to oil-base drilling muds having low fluidloss and increased viscosities. Another aspect of the disclosedinvention pertains to oil-water emulsions used as drilling muds.

U.S. Pat. No. 4,740,319 (Patel, et al.) discloses oil base mudscontaining a “gelling composition” comprising a copolymer which includes2 primary components: (1) latex type material preferably astyrene-butadiene copolymer and (2) one or more functional monomersselected from the group consisting of amides, amines, sulfonates,monocarboxylic acids, dicarboxylic acids and combinations thereof.

In U.S. Pat. No. 5,333,698, a wellbore fluid (e.g., a drilling,completion, packer, or fracturing fluid) is described that includes (a)at least one additive selected from the group consisting of emulsifiers,wetting agents, viscosifiers, weighting agents, fluid loss controlagents, including polymeric fluid loss control agents, proppants for usein hydraulically fracturing subterranean formations, and particulateagents for use in forming a gravel pack; and, (b) a non-toxic whitemineral oil having (i) an API gravity at 15.6° C. (60° F.) greater than35, (ii) a content of compounds containing 14 or more carbon atoms of atleast about 95 weight percent, and (iii) a pour point of at least about−30° C. (−22° F.).

U.S. Pat. No. 5,883,054 to Hernandez, et al., describes thermallystable, oil base drilling fluid systems including drilling fluid and anadditive, wherein the additive includes styrene-butadiene copolymershaving an average molecular weight greater than about 500,000 g/mol, andwherein the drilling fluid system exhibits fluid loss control under hightemperature and high pressure conditions. According to the disclosure,the copolymers were dissolved in the base oil for 16 hours before theremainder of the additives were added.

U.S. Pat. No. 6,730,637 to Stewart, et al. describes a low toxicitydrilling mud oil. In some of the described embodiments, the fluid losscharacteristic of the drilling mud oil as used in a borehole can bereduced to less than 0.2 ml/30 minutes by adding about 0.05% to about2.0% by weight of a butadiene-styrene-butadiene (BSB) block copolymerhaving about 20% by weight or more styrene.

The inventions disclosed and taught herein are directed to polymericcompositions and methods for the use of such compositions for reducingthe fluid loss of invert oil emulsion and all oil well drilling andservicing fluids in which oil is the continuous phase.

BRIEF SUMMARY OF THE INVENTION

The objects described above and other advantages and features of theinvention are incorporated in the application as set forth herein, andthe associated examples and drawings, related to systems for utilizingan oil-soluble polymer in decreasing the fluid loss of oil base muds,particularly such muds that contain little or no aromatic compounds.

The primary purpose of the present invention is to provide a polymericcomposition and methods for use of such compositions for reducing thefluid loss of invert oil emulsion and all oil well drilling andservicing fluids in which oil is the continuous phase, hereinaftersometimes called “oil-base muds” or “oil-base fluids”.

In accordance with a first embodiment of the present disclosure, an oilsoluble polymer is dissolved in an oil to provide a concentrate which isadded to an oil base mud to decrease the fluid loss thereof.

Still another embodiment of the invention provides an additive to reducethe fluid loss of an oil base mud which comprises an oil soluble polymerand an organophilic polyphenolic fluid loss control agent solublized inan oil to form a concentrate.

Another embodiment of the invention provides a method of decreasing thefluid loss of an oil base well drilling or servicing fluid whichcomprises adding to the fluid a first concentrate comprising an oilsoluble polymer dissolved in an oil and a second concentrate comprisingan organophilic polyphenolic material dispersed or solublized in an oil.

In another embodiment of the invention, a method of reducing the loss offluid from an oil base mud is provided which comprises adding asolublized (dissolved) polymer concentrate to an oil base mud.

Yet another embodiment of the invention is to provide a method ofpreparing a concentrate for reducing the fluid loss of an oil base welldrilling or servicing fluid which comprises mixing an oil solublepolymer and an organophilic polyphenolic material in an oil at atemperature in the range from about 150° F. to about 200° F. for 30minutes to about 3 hours at a mixing shear rate of at least about 5,000rpm.

In yet another embodiment of the invention, a method of decreasing thefluid loss of an oil base well drilling or servicing fluid is providedwhich comprises adding to the fluid a first concentrate of an oilsoluble polymer dissolved in an oil as provided hereinbefore and asecond concentrate or an organophilic polyphenolic material, dissolvedor dispersed in an oil. The concentration of the organophilicpolyphenolic material in the second concentrate is from about 0.167grams per milliliter to about 0.348 grams per milliliter of the oil.This second concentrate is prepared by mixing the organophilicpolyphenolic material and the oil together at a temperature in the rangefrom about 150° F. to about 200° F. for 30 minutes to about 3 hours.

In a specific aspect of embodiments of the invention, abutadiene-styrene copolymer is dissolved in a paraffinic hydrocarbon oilto form a concentrate which is added to an oil base mud to decrease thefluid loss thereof.

In another embodiment of the invention, a butadiene-styrene copolymer isdissolved in an oil and an organophilic polyphenolic material, such aslignite, is dissolved or dispersed in the oil to form a concentratewhich can be added to an oil base mud to decrease the fluid losstherefrom.

In yet another embodiment of the present invention, methods of reducinglost circulation in a subterranean well are described, the methodcomprising the steps of preparing a treating composition comprising anoleaginous base fluid, a polymer material having a solubility in theoleaginous base fluid, and one or more organophilic polyphenolicmaterials, the polymer being present in a concentration ranging fromabout 0.03 g/mL of the base fluid to about 0.143 g/mL of the base fluid;injecting the treating composition into the well; and forcing thetreating composition into a lost circulation zone within the well. Inaccordance with aspects of this embodiment, the oleaginous base fluid isa hydrocarbon fluid with a low- or no aromatic content selected from thegroup consisting of crude oil, diesel oil, kerosene, mineral oil,parrafinic hydrocarbon fluid, gasoline, naphtha, and mixtures thereof.

DETAILED DESCRIPTION

The written description of specific structures and functions below arenot presented to limit the scope of what Applicants have invented or thescope of the appended claims. Rather, the written description isprovided to teach any person skilled in the art to make and use theinventions for which patent protection is sought. Those skilled in theart will appreciate that not all features of a commercial embodiment ofthe inventions are described or shown for the sake of clarity andunderstanding. Persons of skill in this art will also appreciate thatthe development of an actual commercial embodiment incorporating aspectsof the present inventions will require numerous implementation-specificdecisions to achieve the developer's ultimate goal for the commercialembodiment. Such implementation-specific decisions may include, andlikely are not limited to, compliance with system-related,business-related, government-related and other constraints, which mayvary by specific implementation, location and from time to time. While adeveloper's efforts might be complex and time-consuming in an absolutesense, such efforts would be, nevertheless, a routine undertaking forthose of skill in this art having benefit of this disclosure. It must beunderstood that the inventions disclosed and taught herein aresusceptible to numerous and various modifications and alternative forms.Further, it will be understood that the compositions described hereincan comprise, consist essentially of, or consist of the statedmaterials. Lastly, the use of a singular term, such as, but not limitedto, “a,” is not intended as limiting of the number of items. Also, theuse of relational terms, such as, but not limited to, “top,” “bottom,”“left,” “right,” “upper,” “lower,” “down,” “up,” “side,” and the likeare used in the written description for clarity in specific reference tothe Figures and are not intended to limit the scope of the invention orthe appended claims.

As used herein, the term “well” includes at least one wellbore. A “well”can include a near-wellbore region of a subterranean formationsurrounding a portion of a wellbore that is in fluid communication withthe wellbore. As used herein, the term “into a well” means at leastthrough the wellhead; it can include into any downhole portion of thewellbore or through the wellbore and into a near-wellbore region.

As used herein, the term “polymer block” means and includes a groupingof multiple monomer units of a single type (i.e., a homopolymer block)or multiple types (i.e., a copolymer block) of constitutional units intoa continuous polymer chain of some length that forms part of a largerpolymer of an even greater length and exhibits a _(X)N value with otherpolymer blocks of unlike monomer types that is sufficient for phaseseparation to occur. For example, the _(X)N value of one polymer blockwith at least one other polymer blocks in the larger polymer may begreater than about 10.

As used herein, the term “block copolymer” means and includes a polymercomposed of chains where each chain contains two or more polymer blocksas defined above and at least two of the blocks are of sufficientsegregation strength (e.g., _(X)N>10) for those blocks to phaseseparate. A wide variety of block polymers are contemplated herein,including but not limited to diblock copolymers (i.e., polymersincluding two polymer blocks), triblock copolymers (i.e., polymersincluding three polymer blocks), multiblock copolymers (i.e., polymersincluding more than three polymer blocks), and combinations thereof.

The term “saturated hydrocarbon”, as used herein, refers to paraffinicand naphthenic compounds, but not to aromatics. Paraffinic compounds maybe either linear (n-paraffins) or branched (i-paraffins). Naphtheniccompounds are cyclic saturated hydrocarbons, i.e. cycloparaffins. Suchhydrocarbons with cyclic structure are typically derived fromcyclopentane or cyclohexane. A naphthenic compound may comprise a singlering structure.

The phrase “high molecular weight hydrocarbons,” in accordance with thepresent invention, refers to those hydrocarbons having an API value (APIgravity) of from 8 to 12° API (and generally a viscosity higher than 350cSt at about 7° C.), while medium molecular weight hydrocarbons have anAPI value of greater than 20° API (for example, from 22 to 30). Theterms “high molecular weight hydrocarbon” and “medium molecular weighthydrocarbon,” as used herein, are terms relative to one another. Theformer term signifies a mixture of hydrocarbons, with or without theirentrained impurities, with an average molecular weight of thehydrocarbons significantly higher than the average molecular weight ofthe hydrocarbons in a medium molecular weight hydrocarbon. Thus, the useof the terms “high molecular weight hydrocarbon” and “medium molecularweight hydrocarbon” does not signify any particular molecular weightranges.

High molecular weight hydrocarbons are typically materials, such ascrude oils, asphaltenes, tars, and heavy oils, which have limited or nopractical use, but which can be converted to more valuable and usefullower molecular weight hydrocarbons via chemical means. Medium oilsgenerally have resins or polar fractions less than about 25% of theweight of the total oil and have an API gravity of 22.3 to 32 withviscosities in the range of about 100 to 1000 centipoise; heavy oilsgenerally have resins or polar fractions between about 25 and 40% of thetotal weight of the oil and have an API gravity of generally above 10but less than 22.3 with viscosities greater than about 1000 centipoise;tars generally have resins or polar fractions greater than about 40% ofthe total weight of the oil and have an API gravity less than about 8 to10 and a viscosity greater than about 8000 centipoise.

The lowest molecular weight hydrocarbons can include C₁ to C₄ gases,e.g., methane, propane, and natural gas. When these gases are present aspart of the lower molecular weight hydrocarbon product, they impart aneven higher API value.

Applicants have created compositions and associated methods forutilizing an oil soluble polymer in decreasing the fluid loss of oilbase muds, particularly such muds containing oils containing low (or no)aromatic compounds. As used herein, the term “fluid loss” refers to theundesirable migration or loss of fluids (such as the fluid portion of adrilling mud or cement slurry) into a subterranean formation or proppantpack. The term “proppant pack”, as used herein, refers to a collectionof a mass of proppant particulates within a fracture or open space in asubterranean formation. Fluid loss may be problematic in any number ofsubterranean operations, including drilling operations, fracturingoperations, well bore clean-out operations, and similar treatmentoperations. In fracturing treatments, for example, fluid loss into theformation may result in a reduction in fluid efficiency, such that thefracturing fluid cannot propagate the fracture as desired.

Oil soluble, polymeric, fluid loss control additives are extremelydifficult to dissolve in a low aromatic content hydrocarbon oil. Thisresults in: (1) poor efficiency as a filtration control additive withoutextensive mixing at elevated temperatures (such as “hot rolling” in alaboratory “roller oven”); (2) extreme viscosity increase of the mudafter the polymer is solublized during circulation of the mud; (3) lossof a considerable quantity of the polymer over solids control screeningequipment due to the particle size of the undissolved polymer; (4) highconcentrations of polymer are required to compensate for theinefficiency and losses of the polymer; and (5) potential formationdamage due to the stickiness and adhesive characteristics of partiallydissolved polymer lodging in producing formation pore openings as aresult of inadequate filtration control.

The concentrate composition of the present invention for reducing theloss of fluid from an oil base mud comprises an oil soluble polymerdissolved in a paraffinic oil. The concentration of polymer in theconcentrate is such that the concentrate is flowable and pumpable atambient temperature, preferably from about 0.03 grams per milliliter ofthe oil to about 0.143 grams per milliliter of the oil. It is preferredthat the Brookfield 8.48 sec¹ shear rate viscosity of a 6.15% wt./vol.concentrate at 40 rpm using a number 2 spindle is from about 300 toabout 500 centipoise.

The preferred oil soluble polymeric fluid loss control additive for usein the invention comprise styrene-butadiene copolymers known in the artas SBR (styrene-butadiene rubber). The styrene content of the SBR ispreferably from about 15% by weight to about 45% by weight of the SBR,more preferably from about 20% to 35% by weight, and most preferablyfrom about 20% to about 25% by weight of the SBR.

It is known to prepare SBR by emulsion polymerization using either a“hot process” or a “cold process.” The hot process is conducted at atemperature of about 50° C. whereas the polymerization in a cold processis about 15° C. to about 20° C. The cold process results in a SBR whichcontains less branching than in the hot process, i.e., the SBR moleculesfrom 10 the cold process contain more linear molecules than the SBR fromthe hot process. It is preferred that the SBR be prepared using a coldprocess. It is also preferred that the SBR not be crosslinked.

The SBR for use in the compositions of this invention must be of thecrumb type (as it is coagulated from the master batch) rather than aground, fine particle size material, in order to obtain the desiredeffect. The particle size of the crumb SBR is less than about 2000micrometers (microns), U.S. Standard Sieve Series (10 mesh screen),preferably from about 2000 micrometers to about 500 micrometers (35 meshscreen), and more preferably from about 2000 micrometers to about 300micrometers (50 mesh screen).

Representative crumb type SBR copolymers can be obtained from ISPELASTOMERS, 1615 Main Street, Port Neches, Tex. 77651 such as thefollowing: Hot Process SBR Elastomers—1006, 1012, and 1013; Cold ProcessSBR Elastomers—8113 and 4503. It is preferred that the Massed MooneyViscosity (MML 1+4 (100° C.)) (“Mooney viscosity”) of the SBR (asdetermined by the American Society of Testing Materials standardprocedure ASTM D1646-96a) be in the range from about 40 to about 140,most preferably from about 105 to about 135. Some other properties ofthe crumb SBR include the following: a free flowing crumb form whicheliminates the need for milling, cutting or grinding; and the crumbparticles retain the porous nature of the coagulated rubber and can bedissolved in a solvent faster than milled or pelletized bale rubber.

Other oil soluble polymers for use in this invention include, but arenot limited to, polystyrene, polybutadiene, polyethylene, polypropylene,and copolymers consisting of at least two monomers selected from thegroup consisting of styrene, butadiene, isoprene, ethene and derivativesthereof, and propylene.

The oil used in the solublized polymer concentrate is preferably anaromatic-free, preferably hydrogenated paraffinic hydrocarbon oil, orsynthetic oil that is aromatic-free. Hydrogenation converts theunsaturated, olefinic carbon-to-carbon bonds to saturated, paraffinicbonds. This results in an oil which is more environmentally acceptable.By aromatic-free is meant herein that the oil contains less than 1volume % aromatic compounds, preferably less than about 0.1 volume %,most preferably no aromatic compounds.

Representative hydrogenated paraffinic oils can be obtained from VASSA,Acientes y Solventes, Venezolanos, S. A., Av. Francisco de Miranda, concalle San Ignacio, Tone 15 Metalica, Piso 3, Chacas, Caracas, Venezuela,such as VASSA™ LP-70, VASSA™ LP-70P, VASSA™ LP-90, VASSA™ LP-100, andVASSA™ LP-120.

The solublized polymer concentrate is prepared by mixing the crumbpolymer and oil together at a temperature in the range from about 65° C.to about 93.3° C. for 30 minutes to about 3 hours at a mixing shear rateof at least about 5,000 rpm. A longer mixing time and a highertemperature can be utilized but are generally unnecessary to thoroughlysolubilize the polymer. The shear rate during mixing must be sufficientto minimize the adherence of the particulate polymer crumbs to oneanother and to the sides of the mixing container as the SBR is veryadhesive.

The solublized polymer concentrate may be used to decrease the fluidloss of oil base well drilling and servicing fluids. Thus, a method ofreducing the fluid loss of an oil base mud comprises adding to the mudthe solublized polymer concentrate in an amount sufficient to providethe fluid with from about 0.5 ppb to about 5 ppb of the polymer.

The oil base mud generally comprises the oil, a suspending agent, and aweighting agent, and optionally a dispersed (emulsified) aqueous phase,emulsifiers, wetting agents, dispersants, and the like as is well knownin the art.

Oils suitable for use in the oil base muds of this invention may beselected from any known oleaginous liquids having a high flash pointsuch as mineral oil, diesel oil, other petroleum fractions, syntheticesters, synthetic ethers, synthetic hydrocarbons such as internalolefins, polyalphaolefins, and the like. Preferred are environmentallyacceptable oils with low toxicity, preferably aromatic-free oils.Particularly preferred are the hydrogenated paraffinic hydrocarbons asset forth hereinbefore.

The emulsifiers used in this invention may be the same emulsifiersgenerally used in water-in-oil invert drilling fluids. These include thevarious fatty acid soaps, including oxidized tall oil soaps, preferablythe calcium soaps whether pre-formed or prepared in-situ in the fluid,polyamides, alkylamidoamines, imidazolines, alkyl sulfonates, fatty acylesters, lecithin, and the like. These include so-called primaryemulsifiers, and secondary emulsifiers.

See, for example the following U.S. Pat. Nos. 2,876,197; 2,994,660;2,962,881; 2,816,973; 2,793,996; 2,588,808; 3,244,638; 4,504,276;4,509,950; 4,776,966; and 4,374,737. Weighting agents as is known in theart can be incorporated in the fluids of this invention. Exemplaryweighting agents or weight materials include barite, galena, ilmenite,iron oxide, siderite, calcite, and the like.

Any of the typically used suspending agents known in the industry can beused. The preferred suspending agent is an organophilic clay(organoclay). Exemplary organoclays are set forth in the following U.S.patents, all incorporated herein by reference: U.S. Pat. Nos. 2,531,427;2,966,506; 4,105,578; 4,208,218. U.S. Pat. No. 5,021,170 disclosesmixtures of an organoclay and a sulfonatedethylene/propylene/5-phenyl-2-norborene terpolymer. Preferredorganoclays are dimethyldi(alkyl)-ammonium bentonite,dimethyldi(alkyl)-ammonium hectorite, methyl-benzyldi(alkyl)ammoniumhectorite, and mixtures thereof.

Any of the typically used fluid loss control additives known in theindustry can be present in the oil base mud, such as gilsonite, asphalt,oxidized asphalt, lignites, and the like. Exemplary organophilicpolyphenolic materials suitable for use as fluid loss control additivesare lignites, as described herein. Particularly preferred arepolyphenolic compounds such as humic acid and the alkali metal saltsthereof (such as found in lignites). Humic acid (HA) is a material ofwide distribution and is present in soils, peat, and coals, particularlylignite or brown coal, and most particularly in the soft brown coalknown as a leonardite. Humic acids are complex organic molecules thatare formed by the breakdown of organic matter. Their exact structuresare generally unknown, and they are extremely variable, often being amixture of different acids containing carboxyl and phenolate groups(such as quinones, phenols, catechols, and the like) so that the mixturebehaves functionally as a dibasic or tribasic add. The principal organicgroups present are phenolic and carboxylic OH, aliphatic CH, carbonyl,conjugated carbonyl or aromatic CH₂ or CH₃ or ionic carboxyl, andpossibly others. The average molecular weight of the humic acids isbetween 5,000 and 50,000.

In accordance with one exemplary embodiment of the present disclosure,the organophilic polyphenolic material is a lignite (amine-treated orotherwise) that exhibits a humic acid (HA) content (as determined bygravimetric analysis or the equivalent), % HA, ranging from about 20% toabout 50%±2% HA; greater than 50% d.b. volatile matter as determined byASTM D3176-09 and D3180; and an average ash content of 15% to 20% d.b.ash (avg.), as determined by ASTM D-3174-12. These requirements havebeen found to contribute to both the solubility of the polyphenolicmaterial, and the fluid loss control properties.

Various other known additives may also be employed in the fluids of thisinvention, if necessary or desired. For example, other wetting agents,corrosion inhibitors, scale inhibitors, and other common additives.

The invention further provides a second polymer concentrate to reducethe fluid loss of oil base muds. This second concentrate comprises anoil, an oil soluble polymer, and an organophilic polyphenolic materialin which the oil soluble polymer is solublized (dissolved) and in whichthe organophilic polyphenolic material is dispersed and/or solubilized.

The concentration of the polymer and the organophilic polyphenolicmaterial in this concentrate are such that the concentrate is flowableand pumpable at ambient temperatures. Preferably the concentration ofthe oil soluble polymer is from about 0.0168 grams per milliliter of theoil to about 0.0348 grams per milliliter of the oil, and theconcentration of the organophilic polyphenolic material is from about0.1677 grams per milliliter of the oil to about 0.3482 grams permilliliter of the oil.

The second polymer concentrate is prepared by mixing the oil solublepolymer, organophilic polyphenolic material, and oil together under thesame temperature and time conditions as set forth hereinbefore for thefirst polymer concentrate. The oil and oil soluble polymer are the sameas set forth hereinbefore for use in the first polymer concentrate. Theorganophilic polyphenolic materials for use in the second polymerconcentrate any number of polyphenolic materials, including those knownin the art as set forth in the following U.S. patents, each incorporatedherein by reference as appropriate: U.S. Pat. No. 3,168,475 (Jordan, etal.); U.S. Pat. No. 3,379,650 (Beasley, et al.); U.S. Pat. No. 3,494,865(Andrews, et al.); U.S. Pat. No. 4,421,655 (Cowan); U.S. Pat. No.4,597,878 (House, et al.,); and U.S. Pat. No. 4,853,465 (Cowan, et al.).In accordance with one aspect of the present disclosure, the preferredorganophilic polyphenolic materials are organophilic lignitic and aminetreated organophilic lignitic (lignite) materials, and amine treatedorganophilic tannins, the polyphenolic materials being treated withamines, particularly quaternary amines, to make the material oildispersible in oil- and synthetic-base muds and fluids.

The second polymer concentrate may also be used to decrease the fluidloss of oil base well drilling and servicing fluids. This method ofreducing the fluid loss of oil base well drilling and servicing fluidscomprises adding to the fluid, or to the oil used in preparing thefluid, the second polymer concentrate in an amount sufficient to providethe fluid with from about 0.5 ppb to about 2.5 ppb of the polymer, andfrom about 5 ppb to about 25 ppb of the organophilic polyphenolicmaterial.

The invention further provides a concentrate of an organophilicpolyphenolic material dissolved and/or dispersed in an oil for theaddition to oil base fluids containing the solublized polymerconcentrate of this invention. When added to oil base fluids containingthe pre-solublized polymer concentrate, the concentrate of theorganophilic polyphenolic material reduces the large viscosity increase(>25%) upon aging the fluids at elevated temperatures as compared whenadding the organophilic polyphenolic material as manufactured, i.e., asa dry powder. The concentration of the organophilic polyphenolicmaterial in this concentrate is from about 0.1677 grams per milliliterto about 0.3482 grams per milliliter of the oil. This concentrate isprepared by mixing the oil and the organophilic polyphenolic materialtogether at a temperature in the range from about 150° F. to about 200°F. for 30 minutes to about 3 hours.

The invert fluids of the invention generally will have an oil to water(O/W or oil:water) volume ratio of from about 40:60 to about 95:5. The“all oil” fluids of the invention will contain less than about 5 volume% aqueous phase, preferably less than about 2 volume %.

The compositions of the present disclosure are useful in preventingfluid loss in certain subterranean formations, during a number ofdifferent subterranean operations, including drilling, completion, andworkover. “Drilling” refers to the events and equipment necessary fordrilling a wellbore. “Completion” refers to the events and equipmentnecessary to bring a wellbore into production once drilling operationshave been concluded, including but not limited to the assembly ofdownhole tubulars and equipment required to enable safe and efficientproduction from an oil or gas well. “Workover” refers to the performanceof major maintenance or remedial treatments on an oil or gas well.

Completion and workover operations may include, but are not limited to,cementing, gravel packing, stimulation, and conformance operations. Manyof these well services are designed to facilitate or enhance theproduction of desirable fluids from or through a subterranean formation.

As used herein, the word “treatment” refers to a treatment for a well orsubterranean formation penetrated by a wellbore that is adapted toachieve a specific purpose in completion or workover, such asstimulation, isolation, or conformance control; however, the word“treatment” does not necessarily imply any particular purpose.

Drilling typically requires the use of a drilling fluid. As used herein,a “drilling fluid” is any of a number of fluids, including fluidmixtures of a liquid with particulate solids or gas (such assuspensions, emulsions, foams) used in operations to drill boreholesinto the earth. The term is synonymous with “drilling mud” in generalusage, although sometimes the term is used to refer to moresophisticated and well-defined “muds.” One classification scheme fordrilling fluids is based on singling out the component that clearlydefines the function and performance of the fluid: (1) water-based, (2)non-water-based, and (3) gaseous (pneumatic). Each category has avariety of subcategories that overlap each other considerably.

A treatment typically involves introducing a treatment fluid into awell. As used herein, a “treatment fluid” is a fluid used to resolve aspecific condition of a wellbore or subterranean formation. As usedherein, a “treatment fluid” also means the specific composition of afluid at the time the fluid is being introduced into a wellbore. Atreatment fluid is typically adapted to be used to achieve a specificpurpose, such as stimulation, isolation, or control of reservoir gas orwater. The word “treatment” in the term “treatment fluid” does notnecessarily imply any particular action by the fluid.

A “spacer fluid” is a fluid used to physically separate onespecial-purpose fluid from another. A special-purpose fluid can be adrilling fluid, a cementing fluid, or a treatment fluid. Special-purposefluids are typically prone to contamination, so a spacer fluidcompatible with each is used between the two. For example, a spacerfluid is used when changing fluid types used in a well. For example, aspacer fluid is used to change from a drilling fluid during drilling awell to a cement slurry during cementing operations in the well. In caseof an oil-based drilling fluid, it should be kept separate from awater-based cementing fluid. In changing to the latter operation, achemically treated water-based spacer fluid is usually used to separatethe drilling fluid from the cement slurry. By way of another example, aspacer fluid can be used to separate two different types of treatmentfluids.

As used herein, a “well fluid” refers to any fluid adapted to be used ina well for a particular purpose, without necessarily implying anyparticular purpose. A “well fluid” can be, for example, a drillingfluid, a cementing fluid, a treatment fluid, or a spacer fluid. As usedherein, a “well fluid” means the specific composition of a fluid at thetime the fluid is being introduced into a wellbore.

The following examples are included to demonstrate preferred embodimentsof the invention. It should be appreciated by those of skill in the artthat the techniques disclosed in the examples which follow representtechniques discovered by the inventor(s) to function well in thepractice of the invention, and thus can be considered to constitutepreferred modes for its practice. However, those of skill in the artshould, in light of the present disclosure, appreciate that many changescan be made in the specific embodiments which are disclosed and stillobtain a like or similar result without departing from the scope of theinvention.

In these examples and this specification, the following abbreviationsmay be used: API=American Petroleum Institute; bbl=42 gallon barrel;ppg=pounds per gallon; gal=gallon; m³=cubic meters; ° F.=degreesFahrenheit; %=percent; kg/m³=kilograms per cubic meter; PV=API plasticviscosity in centipoise (cp); YP=API yield point, measured in pounds per100 square feet (lb/100 ft²); 10″/10′ Gels=10 second/10 minute gelstrengths in pounds per 100 square feet; LSRV=Brookfield low shear rateviscosity at 0.3 revolutions per minute, 0.063 sec⁻¹ in centipoise;vol.=volume; O/W=oil/water ratio, vol/vol; mL=milliliters; g=grams;lb=pounds; cp=centipoise; ft=feet; rpm=revolutions per minute;ES=emulsion stability, in volts; psi=pounds per square inch;mm=millimeter; HTHP=high temperature, high pressure fluid loss, measuredat 200-350° F./500 psi differential and reported as milliliters (mL)/30min, evaluated in accordance with API Bulletin RP 13B-2 1990 or theequivalent (e.g., API Recommended Practice (RP) 131/26.4—“Procedure forHigh Temperature, High Pressure (HTHP) Filtration”).

The plastic viscosity, yield point, and gel strengths were obtained bythe procedures set forth in API's Recommended Practice 13B-1. Using theviscometer as described in API Bulletin RP 13B-1, the viscosity of thefluids was determined by taking readings at 600 rpm, 300 rpm, 200 rpm,100 rpm, 6 rpm, and 3 rpm. The following calculations were made todetermine the Plastic Viscosity (PV) and Yield Point (YP): PlasticViscosity=600 rpm reading minus 300 rpm reading=PV value (in cP); YieldPoint=300 rpm reading minus PV=YP value (in lb/100 ft²). Gel strengthreadings were taken at 10 second, 10 minute, and 30 minute intervals inthe following manner: the viscometer was run at high speed for 10seconds and then the fluid remains static (undisturbed) for 10 seconds.At the end of 10 seconds, the maximum reading running the viscometer at3 rpm was recorded. This procedure was repeated for 10 minute and 30minute gels, the values being given in units of lb/100 ft². The LSRV(low shear rate viscosity) was obtained for the fluids using aBrookfield Model LVTDV-I viscometer having a number 2 or 3 spindle at0.3 revolutions per minute (shear rate of 0.063 sec⁻¹). The LSRV isindicative of the suspension properties of the fluid, the larger theLSRV, the better is the suspension of solids in the fluid. The fluidloss was determined at 300° F. in a modified API HTHP cell at 500 psidifferential pressure utilizing a 3 micron disk (Aloxite™)

In the examples, the oil designated “LP-90E” is the hydrogenatedparaffinic hydrocarbon VASSA™ LP-90 containing 1.56 mL per bbl of theorganoclay activator set forth in U.S. Pat. No. 7,897,544 (Dobson, etal.), incorporated herein by reference, wherein the volume ratio ofpropylene carbonate to tall oil fatty acid is 1:4. The oil designated“SAFRASOL D 80™” is a dearomatized kerosene available from Safra Co.Ltd., P.O. Box 2824, Jeddah 21461, Saudi Arabia. The hydrocarbonpolymers utilized in the examples designated “SBR 1012”, “SBR 8113”,“SBR 1013”, “SBR 1006”, and “SBR 4503” are crumb-type styrene-butadienerubber copolymers available from ISP Elastomers, 1615 Main Street, PortNeches, Tex. 77651. The organophilic polyphenolic material is theorganophilic lignite “Petrolig™” available from Grinding and Sizing Co.,Inc., 7707 Wallisville Road, Houston, Tex. 77020, which is lignite fromTexas. The lignite preferably exhibits a humic acid (HA) content (asdetermined by gravimetric analysis or the equivalent), % HA, rangingfrom about 20% to about 50%±2% HA; greater than 50% d.b. volatile matteras determined by ASTM D3176-09 and D3180; and an average ash content of15% to 20% d.b. ash (avg.), as determined by ASTM D-3174-12.

EXAMPLES Example 1

Sample Preparation

To 0.6354 bbl equivalents (222.4 milliliters or 189.2 grams) of VASSA™LP-90 were added 1.0 mL of propylene carbonate, 5.75 grams of theorganoclay CLAYTONE® IMG 400 (a product of Southern Clay Products,Gonzales, Tex.), 0.1 mL of a secondary emulsifier, 30 mL of a polymerconcentrate containing 0.035 grams per milliliter of <8 mesh SBR 8113crumb and 0.4 grams per milliliter of PETROLIG™ solublized and dispersedin VASSA™ LP-90 oil (mixed 2 hr. at 175° F.), 40 grams of ULTRA CARB 12calcium carbonate bridging agent available from TBC-Brinadd, Houston,Tex., and 352 grams of barite. The oil base mud was mixed with aBrookfield overhead mixer at 5200 rpm for 40 total minutes. The oil basemud was then evaluated for rheological properties and fluid lossproperties as set forth in Table 1.

The polymer concentrate (350 mL) was prepared as follows: (1) Heat 210.3mL of VASSA™ LP-90 oil to 175° F. (79.4° C.) while mixing slowly on aFann™ overhead mixer; (2) Add 140 grams of PETROLIG™ and allow todisperse completely (about 30 seconds at 5200 rpm); (3) With the Fann™overhead mixer at medium/low speed add 12.25 grams of SBR 8113 crumb (<8mesh); (4) Continue mixing for 2 hours at 175° F., increasing the speedof the mixer as the SBR dissolves and the concentrate thickens.

Example 2

An oil base mud such as described in Example 1 was prepared, except thatthe fluid contained 187.4 mL of VASSA™ LP-90, and the 30 mL of thepolymer concentrate used in Example 1 was replaced by 33.6 mL of aconcentrate containing 125 grams of PETROLIG™ (114 mL)dissolved/dispersed in 236 mL VASSA™ LP-90, and 20 mL of a concentratecontaining 5% wt./vol. (0.05 grams/mL) SBR 8113 in VASSA™ LP-90 oil. Thedata obtained is given in Table 2.

Comparative Example A

An oil base mud such as described in Example 1 was prepared, except thatthe fluid contained 213.5 mL of VASSA™ LP-90, and the 30 mL of thepolymer concentrate used in Example 1 was replaced by 21.0 mL of the 5%wt./vol. SBR 8113 crumb concentrate in Example 2 and 12.0 grams ofPETROLIG™ powder. The data obtained is given in Table A.

The data in Table 1 and Table 2 as compared to the data in Table Aindicates that the polymer concentrate containing both the solublizedSBR 8113 crumb copolymer and the solublized/dispersed organolignite(Table 1) or the two concentrates containing the solublized polymer andthe solublized/dispersed organolignite (Table 2) produced oil base mudsexhibiting better fluid loss control and better rheological stabilityafter heating at 300° F. as compared to adding the dry, powderedorganolignite, as exhibited by the HTHP/API fluid loss values of 20 and22 respectively for the two solubilized compositions, compared with theHTHP/API fluid loss value of nearly 32 when the organophilicpolyphenolic material was added in dry, powdered form (i.e., dryblended). This data also shows that the solubilized polymer andsolubilized or dispersed organophilic polyphenolic material incombination perform efficiently as fluid loss control additives for welltreatment or drilling fluids.

Example 3

To 213.5 mL of SAFRASOL D80™ were added 1.0 mL of the organoclayactivator set forth in U.S. Pat. No. 7,897,544 (Dobson et al.), 5.75grams of the organoclay CLAYTONE® IMG 400, 33.0 mL of the polymerconcentrate containing 5.0% wt./vol. SBR 8113 crumb and 36.0% wt./vol.PETROLIG™ solubilized and dispersed in SAFRASOL D80™ (mixed at 175° F.for 2 hrs.), 40.0 grams of ULTRA CARB 12, 353 grams of barite, and 0.1mL of a secondary emulsifier. The oil base mud was mixed as in Example 1and evaluated. The data obtained is set forth in Table 3.

Comparative Example B

To 0.61 bbl equivalents (213.5 mL) of VASSA™ LP-90 oil are added 1.0 mLof propylene carbonate, 5.75 grams of the organoclay CLAYTONE® IMG 400,0.1 mL of a secondary emulsifier, 12.0 grams of PETROLIG™, 21 mL of apolymer concentrate containing 5% wt/vol SBR 1012 crumb (1.05 grams SBR1012), 40 grams of ULTRA CARB 12, and 352 grams of barite to prepare onebbl equivalent (350 mL) of an oil base fluid of this invention. Thefluid was admixed for 30 minutes with an overhead mixer. The oil basefluid was then evaluated for rheological properties and fluid lossproperties as set forth in Table B.

Comparative Examples C, D

Comparative Example B was repeated except that the SBR 1012 was replacedby SBR 1013, and SBR 1006, respectively. The data obtained is set forthin Tables C, and D, respectively. The data in Tables B, C, and D,indicate the large viscosity increase of the oil base fluids containingthe dry organophilic polyphenolic material (lignite powder) upon agingat high temperatures, and in comparison with the data in ComparativeExample A, that the cold processed SBR crumb (SBR 8113) is preferredover the hot processed SBR crumb (SBR 1012, 1013, 1006).

TABLE 1 After Hot Rolling Initial Initial 16 hr. @ 300° F. Temperature,° F. 79 150 150 API Rheology 600 185 98 84 300 108 58 52 200 80 45 40100 49 30 27  6 14 12 11  3 12 11 9 PV 77 40 32 YP 31 18 20 10″/10′ Gels20/37 18/36 14/26 LSRV Peak 65,300 53,200 54,600 2 Minute 65,300 53,20053,300 HTHP Fluid Loss @ 300° F. Spurt, mL 1.0 Trace 30 Minute, mL 9.022.0

TABLE 2 After Hot Rolling Initial Initial 16 hr. @ 300° F. Temperature,° F. 83 150 150 API Rheology 600 210 104 90 300 124 64 53 200 93 49 40100 58 33 26  6 15 13 10  3 11 11 9 PV 86 40 37 YP 38 24 16 10″/10′ Gels17/40 18/45 14/26 LSRV Peak 97,000 60,000 55,700 2 Minute 97,000 60,00055,700 HTHP Fluid Loss @ 300° F. Spurt, mL Trace 30 Minute, mL 20.0

TABLE A After Hot Rolling Initial Initial 16 hr. @ 300° F. Temperature,° F. 82 150 150 API Rheology 600 128 74 132 300 72 42 96 200 51 32 85100 31 21 70  6 7 7 56  3 5 5 55 PV 56 32 36 YP 16 10 60 10″/10′ Gels8/16 9/20 72/85 LSRV Peak 36,200 27,800 89,000 2 Minute 36,200 27,80066,700 HTHP Fluid Loss @ 300° F. Spurt, mL 1.5 4.0 30 Minute, mL 13.031.5

TABLE 3 After Hot Rolling Initial 16 hr. @ 300° F. Temperature, ° F. 85150 API Rheology 600 120 98 300 70 68 200 52 59 100 32 48  6 8 35  3 635 PV 50 30 YP 20 38 10″/10′ Gels 10/26 45/65 LSRV 2 Minute 51,10062,900 HTHP Fluid Loss @ 300° F. Spurt, mL 0 Trace 30 Minute, mL 5.0 8.0

TABLE B SBR 1012 After Hot Rolling Initial Initial 16 hr. @ 300° F.Temperature, ° F. 82 150 150 API Rheology 600 138 78 171 300 78 47 130200 58 35 120 100 35 23 94  6 8 8 74  3 6 7 73 PV 50 47 41 YP 28 31 8710″/10′ Gels 10/20 10/22 88/110 LSRV Peak 51,800 45,200 108,000 2 Minute51,800 45,200 91,200 HTHP Fluid Loss @ 300° F. Spurt, mL Trace Trace 30Minute, mL 13.5 16.5

TABLE C SBR 1013 After Hot Rolling Initial Initial 16 hr. @ 300° F.Temperature, ° F. 82 150 150 API Rheology 600 130 70 153 300 72 40 113200 52 30 103 100 30 18 86  6 7 5 70  3 5 4 70 PV 58 30 40 YP 14 10 7310″/10′ Gels 8/20 7/16 91/95 LSRV Peak 47,300 38,400 259,000 2 Minute47,300 38,400 74,000 HTHP Fluid Loss @ 300° F. Spurt, mL Trace 1.0 30Minute, mL 11.5 26.0

TABLE D SBR 1006 After Hot Rolling Initial Initial 16 hr. @ 300° F.Temperature, ° F. 82 150 150 API Rheology 600 115 66 184 300 64 38 130200 46 28 125 100 28 18 115  6 6 5 91  3 4 4 91 PV 51 28 54 YP 13 10 7610″/10′ Gels 8/19 7/15 105/112 LSRV Peak 41,000 27,300 83,000 2 Minute41,000 27,300 54,800 HTHP Fluid Loss @ 300° F. Spurt, mL Trace 1.0 30Minute, mL 12.5 29.5

Other and further embodiments utilizing one or more aspects of theinventions described above can be devised without departing from thespirit of Applicant's invention. For example, other, equivalent polymersnot listed herein, or co-polymers of such polyphenolic materials, may beused in the compositions without deviating from the scope of thisdisclosure. Further, the various methods and embodiments of the methodsof manufacture and assembly of the system, as well as locationspecifications, can be included in combination with each other toproduce variations of the disclosed methods and embodiments. Discussionof singular elements can include plural elements and vice-versa.

The order of steps can occur in a variety of sequences unless otherwisespecifically limited. The various steps described herein can be combinedwith other steps, interlineated with the stated steps, and/or split intomultiple steps. Similarly, elements have been described functionally andcan be embodied as separate components or can be combined intocomponents having multiple functions.

The inventions have been described in the context of preferred and otherembodiments and not every embodiment of the invention has beendescribed. Obvious modifications and alterations to the describedembodiments are available to those of ordinary skill in the art. Thedisclosed and undisclosed embodiments are not intended to limit orrestrict the scope or applicability of the invention conceived of by theApplicants, but rather, in conformity with the patent laws, Applicantsintend to fully protect all such modifications and improvements thatcome within the scope or range of equivalent of the following claims.

What is claimed is:
 1. A method of reducing fluid loss in a well, themethod comprising: providing a fluid loss prevention concentratecomprising: an oleaginous liquid; a soluble polymer selected fromstyrene-butadiene rubber (SBR) crumb and a styrene-butadiene-styreneblock copolymer crumb; and an amine-treated lignite, preparing atreating fluid by dispersing or dissolving the fluid loss preventionconcentrate within an oil-based drilling fluid so that the concentrationof the soluble polymer in the treating fluid is 0.5 ppb to 5 ppb,injecting the treating into the well, and circulating the treating fluidinto a lost circulation zone of the well so as to form a filter cakecomprising the SBR crumb within the lost circulation zone.
 2. The methodof claim 1, wherein the polymer is a cold-type SBR crumb.
 3. The methodof claim 1, wherein the oleaginous liquid is an aromatic-free,hydrogenated oil consisting essentially of saturated hydrocarbons ofmedium- to high-molecular weight.
 4. The method of claim 1, wherein theconcentration of the polymer is from about 0.0168 grams per milliliter(g/mL) of the oleaginous liquid to about 0.05 g/mL of the oleaginousliquid.
 5. The method of claim 1, wherein the concentration of theamine-treated lignite is from about 0.1677 g/mL of the oleaginous liquidto about 0.3482 g/mL of the oleaginous liquid.